1. Field of the Invention
The present invention relates to a static induction semiconductor device for use as a high-power switching device capable of handling high electric power.
2. Description of the Prior Art
Static induction transistors (SIT), invented by Professor Nishizawa of Tohoku University, Japan, in 1960, have been finding a wide range of applications through many research and development efforts, which have resulted in various excellent static induction semiconductor devices for use as highly efficient high-power devices, image sensors, and high-speed ICs.
One typical static induction transistor is shown in FIG. 6 of the accompanying drawings. As shown in FIG. 6, the conventional static induction transistor includes a low-resistance layer 601 of n-type silicon crystal and a high-resistance layer 602 of n-type silicon crystal which are successively deposited on a drain electrode 612. The conventional static inductor transistor also includes a spaced low-resistance layer 603 of n-type semiconductor crystal which is deposited on the high-resistance layer 602. The low-resistance layer 603 serves as a source region, and the low-resistance layer 601 as a drain region. A p-type gate region 604, which is of a resistance layer 602, is disposed in the high-resistance layer 602 around the source region 603. Protective layers 610 are deposited on the surfaces of the gate region 604 and the source region 603. Source and gate electrodes 611, 613 are disposed in contact with the source and gate regions 603, 604, respectively.
In operation, a current flowing between the source and drain regions 603, 601 is controlled when the condition of a depletion layer in the high-resistance layer 602 is varied by a gate bias applied through the gate electrode 613.
While various high-performance static induction semiconductor devices of silicon crystal have been developed, few research attempts have been made with respect to static induction semiconductor devices made of gallium arsenide (GaAs). In particular, almost no research reports are known with respect to high-power switching devices made of GaAs in the form of static induction semiconductor devices.
To realize high-power switching devices made of GaAs as static induction semiconductor devices, it is necessary to reduce their resistance when they are turned on. To meet such a requirement, they have to operate in a bipolar mode to keep the gate forward-biased. However, it is difficult to operate a GaAs high-power switching device, such as a static induction semiconductor device, in a bipolar mode if it has the conventional structure of a silicon switching device.